Greed and Content

"Examine the record of history, recollect what has happened within the circle of your own experience, consider with attention what has been the conduct of almost all the great unfortunate, either in private or in public life, whom you may have either read of, or heard of, or remember; and you will find that the misfortunes of by far the greater part of them have arisen from their not knowing when they were well, when it was proper fro them to sit still and be contented."  - Adam Smith in The Theory of Moral Sentiments